With recent development in video and audio digitization, a standardization of recording and playback of compressed video and audio data in/from storage media has been promoted. A DVD is one of these standards. Although a DVD has conventionally been used for playback only, a video recording standard for recording video and audio data has been established since a recordable DVD has recently been put to practical use.
Hereinafter, a description will be given of a video recording standard that is discussed in “Transactions of the Institute of Image Information and Television Engineers, Vol. 53, No. 10, “Trends in Standardization of Optical Disk”, Murase et al.”, as an example of a conventional video processing method for video recording and playback, with reference to the drawings.
FIGS. 7(a)–7(d) are diagrams for explaining a video recording standard as an example of a conventional video recording/playback standard. FIG. 7(a) is a block diagram of a recording/playback apparatus, and FIGS. 7(b)–7(d) are diagrams for explaining a recorded video and audio format. In FIG. 7(a), reference numeral 71 denotes a codec unit for compressing video and audio data and multiplexing the compressed video and audio data, or for demultiplexing the compressed and multiplexed video and audio data and decompressing the video and audio data. Reference numeral 72 denotes a drive for recording the data that is generated in the codec unit 71 on a recording medium, or playing the data from the recording medium.
Hereinafter, the operation of the recording/playback apparatus will be described with reference to FIGS. 7(a)–7(d). Digitized video and audio data are supplied from the outside (i.e., externally supplied) to a video codec 711 and an audio codec 712, respectively, and are compressed. The compressed data are inputted to a multiplexer/demultiplexer 713. The data recorded by a DVD are constituted in units of Video Objects as shown in FIG. 7(b), and each Video Object corresponds to a program. Each Video Object is composed of plural Video Object Units as shown in FIG. 7(c), and each Video Object Unit is, for example, a random-accessible unit. Each Video Object Unit is further divided into Video Packs and Audio Packs as shown in FIG. 7(d). A Pack is a unit of actual disk recording and playback, such as 2048 bytes.
The multiplexer/demultiplexer 713 receives the inputted compressed video and audio data and divides them into Packs, assigns time information for synchronous reproduction to each Pack, and then, multiplexes Video Packs and Audio Packs as shown in FIG. 7(d) to output the result to the track buffer 714. Further, the data outputted from the track buffer 714 in the codec 71 are assigned with data for error correction by the error correction unit 721 in the drive 72, modulated by the modulator/demodulator 722, and are then recorded on the DVD-RAM disk 724. On the other hand, the data recorded on the DVD-RAM disk 724 are demodulated and error corrected according to a procedure that is reverse to that of the recording, and are inputted to the multiplexer/demultiplexer 713 through the track buffer 714. Because the inputted data are multiplexed so as to have a format of FIGS. 7(d)–7(d), data is demultiplexed with distinguishing between video and audio by referring to the headers, and the demultiplexed video and audio data are inputted to the video codec 711 and the audio codec 712, respectively, so as to be decompressed and played back.
In the conventional video processing apparatus constructed as described above, the compressed and multiplexed data, which are recorded so as to have a predetermined format, are demultiplexed into video data and audio data and they are played back, thereby performing data recording/playback complying with the video recording standard. However, the construction shown in FIG. 7(a) which operates so as to have formats as shown in FIGS. 7(b)–7(d) has the following two drawbacks.
Firstly, the formats of data which are to be recorded onto a DVD necessarily carries out multiplexing of video and audio as shown in FIG. 7(d). However, carrying out multiplexing of video and audio would be a large load when high-speed data processing is required. In recent years, with the reduction in costs of semiconductor memories, a medium that can perform high-speed data inputting and outputting differently from a DVD, has been recognized as a storage medium. When using a medium such as semiconductor memories which perform high-speed data inputting and outputting, the processing which have been carried out in case of employing a DVD, i.e., multiplexing video data and audio data and alternately recording those on tracks, and reading them by tracing the tracks with a pick-up at a fixed rate, are not required and, moreover, data that are recorded at an arbitrary position on the medium can be taken by employing random access accessing. Thus, data are not necessarily required to be multiplexed, and video and audio data can be apparently simultaneously inputted or outputted. Among multimedia data that are transmitted through the Internet, we can find many of them performing no multiplexing of video and audio data. In view of this, multiplexing and demultiplexing at recording are nothing but applying load to equipment.
Secondly, in MPEG4 (the standard for compression of moving pictures as established by the ISO/IEC in 1999), a plurality of video and audio data can be handled in one program. Then, which video or which audio data are to be played at which position and at which time are expressed by data called “scene description”. In this case, the data to be played are determined by the content of the scene description, and therefore, it was impossible to multiplex plural pieces of video and audio data at predetermined intervals as in the conventional video processing.